1. Field of the Invention
The present invention relates to a zero insertion force connector, in particular to a structural design of the connecting terminals on the connector that can prevent PGA package pins from damaging the plated through holes and poor contacts of solder balls for BGA packages, basing on surface contact to join the zero insertion force connector and the substrate.
2. Description of Related Arts
For Intel""s Pentium(trademark) series of CPU, with the exception of Pentium II(trademark), the new generation of Pentium CPUs has used the zero insertion force connector to mount onto the substrate as shown in FIG. 4. The connector comprises a connector base (70), a sliding cover (71), and a clamping lever (72)
The connector base (70) having multiple connecting terminals (701) in PGA form (as shown in FIG. 5) is to be inserted into corresponding through holes (81) in the substrate (80) and joined with the substrate (80) after soldering the projections on the back side. The connector could also be adapted for solder ball type BGA packages.
The sliding cover (71) is to be placed over the connector base (70), allowing the cover (71) to be shifted horizontally over the surface of the connector base (70). The cover (71) has multiple insertion holes (711) on the surface in array format (as shown in FIG. 4). Each insertion hole (711) is matched by a corresponding connecting terminal (701) on the connector base (70). However, the insertion holes (711) and the connecting terminals (701) on the connector base (70) are in alternately arranged positions before shifting of the sliding cover (71). The cover (71) has to be slid horizontally from the first position to the second position, so that the insertion holes (711) are lined up with the connecting terminals (701) on the substrate (80), and the CPU with the projections are inserted onto the insertion hole (711) of the sliding cover (71). When the cover (71) is initially placed in the first position, the PGA package pins of the CPU are kept separate from the connecting terminals (701), but when the cover (71) is moved into the second position, the PGA package pins can be inserted through the insertion holes (711) and make contact with the connecting terminals (701) for electrical connection.
The clamping lever (72) is installed on the common end of the connector base (70) and the sliding cover (71) on the lateral side, clamping together the opposing faces of the sliding cover (71) and connector base (70) separated by a small distance. The clamping lever (72) is used for securing the sliding cover to prevent any horizontal shifting after mounting of the connector.
The mechanical components and the operating principles of the zero insertion force connector have been widely publicized in related literature, so this part therefore will not be further discussed. The focus of the present disclosure is on how to install the zero insertion force connector onto the substrate with good reliability and the structure associated therewith.
A typical connecting terminal (701) of zero insertion force connector for a pin grid array (PGA) package, as shown in FIG. 5, are designed with the connecting terminals (701) directly inserted into the substrate (80) through the plated through holes (81). Since the projected ends of the connecting terminals (701) are quite sharp, the pointed terminals (701) often cause physical damage to the electroplated layer on the through holes (81), thereby affecting the electrical performance of the substrate (80).
Another kind of commonly used zero insertion force connector is constructed for ball grid array (BGA) packages (as shown in FIG. 6). The connecting terminals (701) of this kind of package are connected to the substrate by means of solder balls. These solder balls acting as terminals are so tiny and densely packed in a relatively small grid that an abnormal phenomenon will develop when the surface of the substrate (80) is not smooth. That is, a small portion of the solder balls cannot form solid contact with the solder pads on the substrate.
Thus the installation of zero insertion force connectors on the substrate, for both PGA and BGA packages, still has certain flaws using the conventional techniques mentioned above. There are risks of damaging the internal circuit on the substrate for PGA packages and poor electrical contact for BGA packages. To overcome the above-mentioned situations an improved connecting apparatus and technique is needed.
The main object of the present invention is to provide a zero insertion force connector that is capable of preventing physical damage to the internal circuit connected through plated through holes as well as eliminating poor contacts for ball grid array packages.
The zero insertion force connector in accordance with the present invention comprises:
a connector base having multiple connecting terminals in array format;
a sliding cover which can shift horizontally over the connector base into predetermined position; and
a clamping lever with an xe2x80x9cLxe2x80x9d shape construct, the horizontal portion of which is fixed on the common end of the connector base, used for clamping against the sliding cover to prevent the cover from shifting in the horizontal direction.
Each connecting terminal on the connector base is formed as in a strip having one end bent to form a contact plate matching against the circuit junctions at predetermined positions on the substrate.
When the connector is appropriately placed over the substrate and a small amount of pressure is applied, the connecting terminals come into contact with the circuit junctions on the substrate, so that the connector can join with the substrate with good reliability after soldering of the joints at the back of the substrate has been performed.
The lower portion of the connecting terminals forming the contact plate is bent at a predetermined angle to ensure good contact with the corresponding pad on the substrate.
The features and structure of the present invention will be more clearly understood when taken in conjunction with the accompanying figures.